Piston and cylinder device

ABSTRACT

The invention is a device for filling and emptying pipettes which is particularly applicable to situations where it is desired to take a large number of samples each of which is of identical volume. The device comprises a piston and cylinder arrangement which is arranged to be releasably sealed to the end of a pipette, the device being actuated by depressing a piston rod against the action of a spring. The effective stroke of the piston is variable, so as to adjust the amount of liquid induced into the pipette, by arranging the piston rod in two parts which are in screw-threaded engagment one with the other, whereby the length of the piston rod can be altered.

United States Patent 1 91 Poulten 1451 May 7,1974

[ 4] Prs'roN AND CYLINDER DEVICE [75] Inventor: John H. Poulten, Upminster,

England [73] Assignee: John Poulten Limited, Barking,

Essex, England [22] Filed: Feb, 13, 1973 [21] Appl. No.: 332,220

[30] Foreign Application Priority Data 2,799,437 7/1957 .lepson 222/481 Primary Examiner-Stanley H. Tollberg Assistant Examiner-Larry H. Martin 9 Attorney, Agent, or FirmBrady, OBoyle & Gates [5 7] ABSTRACT The invention is a device for filling and emptying pipettes which is particularly applicable to situations where it is desired to take a large number of samples each of which is of identical volume. The device comprises a piston and cylinder arrangement which is arranged to be releasably sealed to the end of a pipette, the device being actuated by depressing a piston rod against the action of a spring; The effective stroke of the piston is variable, so as to adjust the amount of liquid induced into the pipette, by arranging the piston rod in two parts which are in screw-threaded engag- -ment one with the other, whereby the length of the piston rod can be altered.

7 Claims, 7 Drawing Figures [56] References Cited UNITED STATES PATENTS 951,160 3/1910 Wanwright... 128/236 273x905 3/1956 .0150 ..222/390x PATENTEDMAY 71974- SHEET 2 BF 2 FIG.3.

. l PISTON AND CYLINDER DEVICE The present invention relates to a piston and cylinder device for filling and emptying Containers such, for example, as pipettes.

Piston and cylinder devices for filling and emptying pipettes have already been proposed in which the piston is moved by means of a rack and pinion device to by rotating the pinion in the opposite direction to that employed when filling the pipette.

The disadvangage of such devices is that the size of the device is altered during charging and discharging of the pipette, thus making one-handed operation of the device extremely difficult.

It is an object of the present invention to overcome or at least mitigate the above disadvantage.

The present invention provides a piston and cylinder device for filling and emptyingcontainers comprising means for changing the effective stroke of the piston.

Preferably, the stroke of the piston is .changed by varying the length of the piston rod.

Preferably the means for changing the lengthof the piston rod comprises a piston rod which is attached to the piston and which is in threadedengagement with a second rod member, which is rotatable relative thereto, axial movement of the second rod member in a direction away from the piston being limited by stop means. The piston rod is advantageously provided with guide means associated with a guide plate which is arranged to close one end of the" cylinder toprevent rotation of the piston rod relative to the cylinder. The other end of the cylinder" is provided with an opening which is adapted for fluid-tight engagement with one end of the container.

A cover may be attached to the cylinder with the guide plate interposed between the cover and the cylinder, an actuator memberwhich is secured to the second rod member projecting through an opening in the end of the cover remote from the cylinder. The piston is preferably resiliently biassed into a rest position, in which the stop means is in contact with the cover for example by means of a helicalspring. lnthis position the piston is remote from the end of the cylinder having the opening for communication with the container.

An orifice may be provided in the cylinder adjacent to the opening for engagement with said'one end of the container for allowing the portion of the cylinder swept by the piston to be opened to the atmosphere during use of the device.

Preferably, the opening in the cylinder for fluid-tight engagement with said one end of the container is provided with resilient sealing means.

In order that the present invention be more readily ,understood embodiments thereof will now be de- FIG. 2b is an underneath view of the sealing member of F 16. 2a;

FIG. 3 is a side view of a modified form of piston and cylinder device;

- draw liquid into the pipette, the liquid being discharged FIG. 4a is a sectional side view of a modified form of sealing member for use with the device of FIG. 1 or FIG. 4b is an underneath plan view of the sealing member of FIG. 4a, and

FIG. 5 is a perspective view of part of the device of FIG. 3. r

shown-in FIG. 1, a piston and cylinder device comprises a cylinderical body 1 which defines a piston chamber and which is connected to a generally cylindrical cover 2 by a threaded collar 3.

A piston 5 of an elastomeric substance, which is mounted on a support flange (not shown), is slidably received in the positon chamber and is secured to a first piston rod 6 which is generally cylindrical but which has two radially extending fins 8 which are disposed div ametrically opposite one another. The piston rod 6 projects through an aperture in a guide plate 9 interposed between, and maintained in position by, the body 1 and the cover 2. The shape of the aperture in the guide plate 9 corresponds to the cross-sectional shape of the piston rod 6- so that the member 6 is constrained to move axially without being able to rotate about the axis of the member 6. Y

An axially extending threaded bore 11 is provided in the free end of the piston rod and received a correspondingly externally threaded rod 12 which is attached to an actuator member in the form of a knurled control knob 13 which is provided at its lower end with a stop flange 14. The knob 13 projects through a hole in the top of the cover 2 and the flange 14, which is larger in diameter than the hole, is urged against the inner surface of the cover 2 by a helical spring 16 dis posed between the guide plate 9 and the flange 14.

The body 1 is provided at its lower end with an orifice 20 which is normally closed by a screw threaded cap 32 and with an opening 21 by means of which the piston chamber is in communication with one end of a pipette or other graduated tube 31, which is shown .in dotted lines in FIG. 1. The opening 21 is defined by a tubular extension 22, the free end of which is formed with an external screw thread for engagement with a collet 23 which together with elastomeric sealing member 24 sealsthe piston, chamber 1 to the pipette.

The sealing member 24 is tubular and comprises a section 25, which is arranged to be received within the tubular extension 22, an annular shoulder 26 which is adapted to rest against the end of the tubular extension 22, and a further tubular section 23 of greater external diameter than the section 25 and which is arranged to be received in a frusto-conical portion 30 of the collet As will be seen from FIG. 2b, the section 28 is elliptically shaped externally and has a bore which is circular in cross-section such that the walls of the section 28 have two relatively thin portions which constrain the section 28 to form a pair of lips defining a slit for receiving the end of the pipette when the collet 23 is screwed onto the extension 22.

An alternative but generally similar form of elastomeric sealing member 24 is shown in FIGS. 4a and 4b In one method of use, the tubular end 31 of a pipette is pressed into the sealing member 24, and the collet 23 is tightened by rotating it relative to the body 1 so that the lips of the device sealingly grip the end 31 of the pipette. The tip of the pipette is then dipped into a liquid to be drawn up into the pipette-The control knob 13 is then rotated to screw the rod 12 into the piston rod 6. Since the knob 13 is urged against the cover 2 by the spring 16, the piston 5 is moved upwardly to draw liguid into the pipette. Once the desired amount of liquid has been collected it can be discharged by depressing the knob 13 against the action of the spring 16 to discharge the liquid quickly when the pipette is of the fast flow type. Alternatively the knob 13 can be rotated in the opposite direction to that previously mentioned so as gradually to push the piston downwards. This allows the pipette/piston and cylinder combination to be used in the manner of a bure ttefor titrations, i.e. where the liquid is discharged one drop at a time. By arranging for a suitable number of screw threads on the rod 12 and the rod member 6- it is easy to dispense accurately only one drop of liquid at a time;

Yet another method of discharging the liquidfrom the pipette is by partially unscrewing the cap 32 over the orifice 20 to allow air at atmospheric pressure to enter the cylinder so thatthe liquid in the pipette can flow freely out. This feature allows the device to be used with those pipettes which are calibrated on the basis that the liquid will not be forced out under pressure.

An alternate form of device for discharging liquid 2 from the pipette comprises a spring clip 33 which has a pair of jaws 37 which snap onto the extension 22, a pair of lugs 36 on the extension 22 maintaining the clip against the under surface of the body 1. The clip 33 has a cap portion 35 which engages over the orifice 20 and seals the orifice, and an extension 34 adapted to be pressed downwardly by the operator to deform the clip and move the cap out of engagement with the orifice 20 so as to allow air into the piston chamber. The clip is preferably made from a hard, resilient plastics material such as nylon. The sealing surface of the cap 35 is preferably lined with a soft elastic material such as rubber.

It will be appreciated that if the pipette is filled by first depressing the knob 1-3, then dipping the pipette into the liquid to be sampled and subsequently releasing the knob so that the piston returns to its rest position under the action of the spring, then if the pipette is subsequently discharged by depressing the knob 13 or by opening the orifice 20 to atmosphere (as distinct from rotating the knob 13), the volume of liquid drawn into the pipette will remain approximately constant for each suction stroke of the piston 5. This means that a number of equal individual volumes of liquid can be drawn up into and discharged from the pipette quickly and accurately, and that only fine adjustment of the volume of liquid by rotating the knob 13 is required.

Since the uppermost position of the knob 13 is limitedby thestop flange 14 it will be obvious that the height of the device is limited and hence the device can be designed so thatit can be used one-handed with ease.

The device is preferably made from plastics material or any'other suitable material which can be autoclaved.

I claim:

l. A piston and cylinder device for filling and emptying containers comprising a piston rod which is attached to the piston, a second rod member connected in threaded engagement with and rotatable relative to said piston rod, stop means connected to limit axial movement of said second rod member in a direction away from the piston, a quide plate arranged to close one end of said cylinder, guide means associated with said piston rod and guide plate and being effective to preventrotation of said piston rodrelative to the cylinder, a cover attached to the cylinder with said guide plate interposed between the cover and the cylinder, and an actuator member secured-to said second rod member and which projects through an opening in the end ,of said cover remote from the cylinder.

2. A piston and cylinder device according to claim 1, wherein the piston is resiliently biassed into a rest position in which the stop means is in contact with the cover.

3. A piston and cylinder device according to claim 1, wherein the piston chamber is formed with an aperture by means of whichthe chamber can be opened to atmosphere and comprising means for closing the aperture.

4. A piston and cylinder device for filling and emptying pipettes, comprising a piston rod attached to the piston, a second rod member in screw-threaded engagement with the piston rod so as to be rotatable relative to the piston rod, stop means on the second rod member for limiting axial movement of the rod member in a direction away from the piston, a guide plate arranged to close one end of the cylinder, guide means.

on the piston rod cooperating with the guide plate to prevent rotation of the piston in the cylinder, a cover attached to the said one end of the cylinder and having an opening in its end remote from the cylinder through which the end of the second rod member projects, resilient means biasing the stop means into contact with the cover, and means for sealing the end of a pipette to the device with the interior of the pipette in communication with the chamber defined by the piston and cylin der. l

5. A piston and cylinder device according to claim 4, wherein the sealing means comprises a tubular elastomeric member adapted to embrace the end of the pipette and having a sealing part formed with at least two radially spaced relatively thick wall portions which are separated by relatively thin wall portions, and means for deforming the sealing part into sealing engagement with the pipette.

6. A piston and cylinder device according to claim 5, wherein the means for deforming the sealing part of the tubular elastomeric member is a housing in screwthreaded engagement with the end of the cylinder so as to surround the sealing means, the housing being formed. with a conical bore which bears against the sealing part and causes inwards deformation thereof when the housing is screwed onto the cylinder.

7. A piston and cylinder device according to claim 4, wherein the piston chamber is formed with an aperture by means of which the chamber can be vented to atmosphere, and comprising means for closing the aperture, the means having a cap seated over the'apertur'e and resiliently biased into contact with the aperture by a spring member mounted on the cylinder, and an operating portion rigid with the cap and which can be enerture. 

1. A piston and cylinder device for filling and emptying containers comprising a piston rod which is attached to the piston, a second rod member connected in threaded engagement with and rotatable relative to said piston rod, stop means connected to limit axial movement of said second rod member in a direction away from the piston, a quide plate arranged to close one end of said cylinder, guide means associated with said piston rod and guide plate and being effective to prevent rotation of said piston rod relative to the cylinder, a cover attached to the cylinder with said guide plate interposed between the cover and the cylinder, and an actuator member secured to said second rod member and which projects through an opening in the end of said cover remote from the cylinder.
 2. A piston and cylinder deviCe according to claim 1, wherein the piston is resiliently biassed into a rest position in which the stop means is in contact with the cover.
 3. A piston and cylinder device according to claim 1, wherein the piston chamber is formed with an aperture by means of which the chamber can be opened to atmosphere and comprising means for closing the aperture.
 4. A piston and cylinder device for filling and emptying pipettes, comprising a piston rod attached to the piston, a second rod member in screw-threaded engagement with the piston rod so as to be rotatable relative to the piston rod, stop means on the second rod member for limiting axial movement of the rod member in a direction away from the piston, a guide plate arranged to close one end of the cylinder, guide means on the piston rod cooperating with the guide plate to prevent rotation of the piston in the cylinder, a cover attached to the said one end of the cylinder and having an opening in its end remote from the cylinder through which the end of the second rod member projects, resilient means biasing the stop means into contact with the cover, and means for sealing the end of a pipette to the device with the interior of the pipette in communication with the chamber defined by the piston and cylinder.
 5. A piston and cylinder device according to claim 4, wherein the sealing means comprises a tubular elastomeric member adapted to embrace the end of the pipette and having a sealing part formed with at least two radially spaced relatively thick wall portions which are separated by relatively thin wall portions, and means for deforming the sealing part into sealing engagement with the pipette.
 6. A piston and cylinder device according to claim 5, wherein the means for deforming the sealing part of the tubular elastomeric member is a housing in screw-threaded engagement with the end of the cylinder so as to surround the sealing means, the housing being formed with a conical bore which bears against the sealing part and causes inwards deformation thereof when the housing is screwed onto the cylinder.
 7. A piston and cylinder device according to claim 4, wherein the piston chamber is formed with an aperture by means of which the chamber can be vented to atmosphere, and comprising means for closing the aperture, the means having a cap seated over the aperture and resiliently biased into contact with the aperture by a spring member mounted on the cylinder, and an operating portion rigid with the cap and which can be engaged by an operator to urge the cap away from the aperture. 